We
all want to use less energy whether it be to reduce greenhouse gases or
to reduce our dependence on foreign oil. This article helps you
decide which type of HDTV to get based on energy consumption. Sets
considered are liquid crystal displays (LCD), digital light
processors (DLP) and plasma TV screens at 720p, 1080p,
1080i and other combinations.

Types of HDTV Technology:

DLP: (Digital
Light Processing) A data projection
technology from TI that produces clear, readable images on screens in
lit rooms. DLP is used in all types of projection devices, from data
projectors that weigh only a few pounds to large rear-projection TVs to
electronic cinema projectors for movie theaters.

DMD "Digital Micromirror Device"
a spatial modulator on a "chip" similar to digital memory. The
DMD
covered with hinged, microscopic electromechanical mirrors, one for
each pixel on the screen. A 1280x1024 resolution DMD has more than a
million "micromirrors," which tilt 10 degrees forward or backward,
acting as light switches. Each mirror is 16 micrometers square, and all
of them fit on a CMOS chip the size of a postage stamp. Tilt the
mirror one way and the pixel is "on." Tilt the mirror the other
way
and the pixel is "off." Gray scale (gradations in color) is
achieved
by modulating the time the mirrors spend between on and
off. For a
one-chip projector, color is achieved by beaming red, green and
blue light onto the DMD chip sequentially. The light source is usually
a
mercury vapor lamp shining through a spinning color wheel or from three
LEDs. LED based DLPs offer longer life and can save power since
less energy is lost to heat making light with LEDs compared to
lamps..

DLP lamps wear out and cost about $300 to replace. A DLP display
is cheaper to buy, inch for inch, but when you add in the extra
electricity and replacement bulb costs, an LCD display of the same size
can cost the same over the lifetime of the display. The LCD has
the added benefit of being "greener."

LCD: (Liquid
Crystal Display)
is a display technology that uses rod-shaped liquid crystal molecules
that flow like a liquid and bend light in the presence of an electric
field. When no electric field is present (unenergized) the
crystals
direct light through two polarizing filters that allow the natural
background color to show. When energized, they redirect the light to be
absorbed in one of the
polarizers, causing the dark appearance of crossed polarizers to show.
The more the molecules are twisted, the better the contrast and viewing
angle.

Because it takes less power to move molecules than to energize a
light-emitting device, be it LEDs or lamps in DLP TVs LCDs are
"greener" thus better for saving energy and the environment. LCDs
replaced the light-emitting diodes (LEDs)
in digital watches in the 1970s and LCD displays replaced CRT (cathode
ray tube) displays for
PCs in the 2000s. LCDs are slowly replacing DLP and Plasma
TVs as
larger screens get more cost effective.

The light source in an active-matrix LCD monitor is a flourescent bulb,
which emits white light through a polarized glass pane behind the
liquid crystal solution. To achieve a full color pallet on your LCD
display, each pixel is divided into three subpixels-red, green, and
blue. The RGB subpixels are created by subtracting certain wavelengths
with filters. By exploiting a combination of red, green, and blue
subpixels of various intensities (or gray scales), a single LCD pixel
triad can reproduce approximately 16.8 million colors. Future
generations of LCD displays may replace the flourescent
light source with an even more energy efficient LEDs.
LCDs use a non-reflective screen which is a significant advantage in a
bright room

Plasma:
Plasma is one of four states of matter (solid, liquid, plasma and
gas). A plasma display is a flat-screen "gas discharge"
technology
that uses tiny cells lined with phosphor that
are full of inert ionized gas (typically a mix of xenon and neon).
Three RGB (one cell has red phosphor, one green,
one blue) cells make up one pixel . The cells are sandwiched between x-
and y-axis panels. A
cell is turned on by charging the appropriate x and y electrodes. The
charge causes the gas in the cell to emit ultraviolet light, which
causes the phosphor to emit color. The amount of charge determines the
intensity, and the combination of the different intensities of red,
green and blue produce all the colors required. The plasma
technology
is similar to the way neon signs work combined
with the red, green and blue phosphor technology of a CRT. Plasma
monitors consume significantly more current than LCD-based monitors.so
they are not nearly as "green" or good fo rthe environment.